Polyamide resin-type composite material and method of producing same

Abstract

A xylylenediamine-based polyamide resin/fiber composite material and molding are provided that do not exhibit a decline in properties under high temperatures and high humidities, and that exhibit a high elastic modulus and present little warping, and exhibit better recycle characteristics, a better moldability, and a better productivity than for thermosetting resins. The polyamide resin-type composite material comprises a fibrous material (B) impregnated with a polyamide resin (A) wherein at least 50 mole % of diamine structural units derived from xylylenediamine, and having a number-average molecular weight (Mn) of 6,000 to 30,000, and containing a component of a molecular weight of not more than 1,000 at 0.5 to 5 mass %.

1 . A polyamide resin-type composite material, comprising a fibrous material (B) impregnated with a polyamide resin (A) comprising at least 50 mole % of diamine structural units derived from a xylylenediamine and 0.5 to 5 mass % of a component with a molecular weight of not more than 1,000, wherein the polyamide resin (A) has a number-average molecular weight (Mn) of 6,000 to 30,000. 
     
     
         2 . The material of  claim 1 , wherein a cyclic compound content of the polyamide resin (A) is 0.01 to 1 mass %. 
     
     
         3 . The material of  claim 1 , wherein a molecular weight distribution (Mw/Mn) of the polyamide resin (A) is 1.8 to 3.1. 
     
     
         4 . The material of  claim 1 , wherein a melt viscosity of the polyamide resin (A) is 50 to 1,200 Pa·s, when measured at the temperature of a melting point of the polyamide resin (A)+30° C., at a shear rate of 122 sec −1 , and at a moisture content in the polyamide resin (A) of not more than 0.06 mass %. 
     
     
         5 . The material of  claim 1 , wherein a flexural modulus retention rate by the polyamide resin (A) upon moisture absorption is at least 85%. 
     
     
         6 . The material of  claim 1 , wherein the polyamide resin (A) has at least two melting points. 
     
     
         7 . The material of  claim 1 , wherein the xylylenediamine is metaxylylenediamine, para-xylylenediamine, or a mixture thereof. 
     
     
         8 . The material of  claim 1 , wherein an average fiber length of the fibrous material (B) is at least 1 cm. 
     
     
         9 . The material of  claim 1 , wherein the fibrous material (B) comprises a functional group reactive with the polyamide resin (A) at a surface thereof. 
     
     
         10 . The material of  claim 9 , wherein the functional group reactive with the polyamide resin (A) is a functional group derived from a silane coupling agent. 
     
     
         11 . The material of  claim 1 , wherein the fibrous material (B) is selected from the group consisting of a glass fiber, a carbon fiber, an inorganic fiber, a plant fiber, and an organic fiber. 
     
     
         12 . The material of  claim 1 , wherein a polyamide resin (A)/fibrous material (B) area ratio in a cross section of the material is from 20/80 to 80/20. 
     
     
         13 . The material of  claim 1 , wherein a void area ratio in a cross section of the material is not more than 5%. 
     
     
         14 . The material of  claim 1 , wherein the polyamide resin (A) further comprises short fibers (D) of the fibrous material (B). 
     
     
         15 . The material of  claim 14 , wherein an average fiber diameter of the short fibers (D) is smaller than an average fiber diameter of the fibrous material (B). 
     
     
         16 . A method for producing a polyamide resin-type composite material, the method comprising:
 converting a polyamide resin (A) comprising at least 50 mole % of diamine structural units derived from a xylylenediamine and 0.5 to 5 mass % of a component with a molecular weight not more than 1,000 into a film or fiber;   stacking a fibrous material (B) and a polyamide resin (A) that has been converted into a film or fiber to form a stacked material; and then   applying heat and pressure to the stacked material to impregnate the polyamide resin (A) into the fibrous material (B),   wherein the polyamide resin (A) has a number-average molecular weight (M) of 6,000 to 30,000.   
     
     
         17 . The method of  claim 16 , wherein impregnating the polyamide resin (A) into the fibrous material (B) occurs in a heated atmosphere by successively applying pressure with a plurality of rolls. 
     
     
         18 . The method of  claim 16 , wherein:
 a heat capacity of crystallization for a polyamide resin (A) that has been converted into a film or fiber is at least 5 J/g; and   a heat capacity of crystallization for a polyamide resin (A) in the obtained polyamide resin-type composite material is at least 5 J/g.   
     
     
         19 . The method of  claim 16 , wherein a film surface roughness (Ra) of a polyamide resin (A) that has been converted into a film is from 0.01 to 1 μm. 
     
     
         20 . The method of  claim 16 , wherein a polyamide resin (A) that has been converted into a fiber is a multifilament, and a monofilament fineness thereof is from 1 to 30 dtex. 
     
     
         21 . The method of  claim 16 , wherein a polyamide resin (A) that has been converted into a fiber is a multifilament having a tensile strength from 1 to 10 gf/d. 
     
     
         22 . The method of  claim 16 , comprising converting the polyamide resin (A) into a film, wherein said film is produced from a coextruded film of the polyamide resin (A) and a polyolefin resin (C) by peeling a polyolefin resin (C) layer from the coextruded film. 
     
     
         23 . The method of  claim 16 , wherein a moisture content of a polyamide resin (A) that has been converted into a film or fiber is from 0.01 to 0.15 mass %. 
     
     
         24 . A method for producing a molding, method comprising heating a polyamide resin-type composite material obtained by the method of  claim 16 , and then molding at a temperature of 70 to 150° C. in a die or with a roll, to form a molding. 
     
     
         25 . The method of  claim 24 , further comprising forming a polyamide resin layer on a surface of the molding.